US11650506B2 - Film structure for electric field guided photoresist patterning process - Google Patents

Abstract

Methods and apparatuses for minimizing line edge/width roughness in lines formed by photolithography are provided. In one example, a method of processing a substrate includes applying a photoresist layer comprising a photoacid generator to on a multi-layer disposed on a substrate, wherein the multi-layer comprises an underlayer formed from an organic material, inorganic material, or a mixture of organic and inorganic materials, exposing a first portion of the photoresist layer unprotected by a photomask to a radiation light in a lithographic exposure process, and applying an electric field or a magnetic field to alter movement of photoacid generated from the photoacid generator substantially in a vertical direction.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application Ser. No. 62/794,298 filed Jan. 18, 2019, which is incorporated by reference in its entirety.

BACKGROUNDField

The present disclosure generally relates to methods and apparatuses for processing a substrate, and more specifically to methods and apparatuses for enhancing photoresist profile control.

Description of the Related Art

Integrated circuits have evolved into complex devices that can include millions of components (e.g., transistors, capacitors and resistors) on a single chip. Photolithography may be used to form components on a chip. Generally the process of photolithography involves a few basic stages. Initially, a photoresist layer is formed on a substrate. The photoresist layer may be formed by, for example, spin-coating. The photoresist layer may include a resist resin and a photoacid generator. The photoacid generator, upon exposure to electromagnetic radiation in the subsequent exposure stage, alters the solubility of the photoresist in the development process. The electromagnetic radiation may have any suitable wavelength, such as a wavelength in the extreme ultra violet region. The electromagnetic radiation may be from any suitable source, such as, for example, a 193 nm ArF laser, an electron beam, an ion beam, or other source. Excess solvent may then be removed in a pre-exposure bake process.

In an exposure stage, a photomask or reticle may be used to selectively expose certain regions of a photoresist layer disposed on the substrate to electromagnetic radiation. Other exposure methods may be maskless exposure methods. Exposure to light may decompose the photoacid generator, which generates acid and results in a latent acid image in the resist resin. After exposure, the substrate may be heated in a post-exposure bake process. During the post-exposure bake process, the acid generated by the photoacid generator reacts with the resist resin in the photoresist layer, changing the solubility of the resist of the photoresist layer during the subsequent development process.

After the post-exposure bake, the substrate, and, particularly, the photoresist layer may be developed and rinsed. After development and rinsing, a patterned photoresist layer is then formed on the substrate, as shown inFIG.1.FIG.1 depicts an exemplary top sectional view of thesubstrate100 having the patternedphotoresist layer104 disposed on atarget material102 to be etched.Openings106 are defined between the patternedphotoresist layer104, after the development and rinse processes, exposing theunderlying target material102 for etching to transfer features onto thetarget material102. However, inaccurate control or low resolution of the lithography exposure process may cause in poor critical dimension of thephotoresist layer104, resulting in unacceptable line width roughness (LWR)108. Furthermore, during the exposure process, acid (shown as inFIG.1) generated from the photoacid generator may randomly diffuse to any regions, including the regions protected under the mask unintended to be diffused, thus creating undesired wigging orroughness profile150 at the edge or interface of the patternedphotoresist layer104 interfaced with theopenings106. Large line width roughness (LWR)108 andundesired wiggling profile150 of thephotoresist layer104 may result in inaccurate feature transfer to thetarget material102, thus, eventually leading to device failure and yield loss.

Therefore, there is a need for a method and an apparatus to control line width roughness (LWR) and enhance resolution as well as dose sensitivity so as to obtain a patterned photoresist layer with desired critical dimensions.

SUMMARY

Embodiments of the present disclosure include a method for forming a film structure to efficiently control of distribution and diffusion of acid from a photoacid generator in a photoresist layer during an exposure process or a pre- or post-exposure baking process. In one example, a device structure includes a film structure disposed on a substrate, and a plurality of openings formed in the film structure, wherein the openings formed across the substrate has a critical dimension uniformity between about 1 nm and 2 nm.

In another embodiment, a method of processing a substrate includes applying a photoresist layer comprising a photoacid generator to on a multi-layer disposed on a substrate, wherein the multi-layer comprises an underlayer formed from an organic material, inorganic material, or a mixture of organic and inorganic materials, exposing a first portion of the photoresist layer unprotected by a photomask to a radiation light in a lithographic exposure process, and applying an electric field or a magnetic field to alter movement of photoacid generated from the photoacid generator substantially in a vertical direction.

In yet another embodiment, a method of processing a substrate includes applying a photoresist layer on an underlayer disposed on a substrate, exposing a first portion of the photoresist layer unprotected by a photomask to a radiation light in a lithographic exposure process, performing a baking process on the photoresist layer and the underlayer, and applying an electric field or a magnetic field while performing the baking process.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

FIG.1 depicts a top view of an exemplary structure of a patterned photoresist layer disposed on a substrate conventionally in the art;

FIG.2 is a schematic cross-sectional view of an apparatus for processing a substrate, according to one embodiment;

FIG.3 is a top view of one embodiment of an electrode assembly disposed in the apparatus ofFIG.2;

FIG.4 depict an acid distribution control of a photoresist layer disposed on a film structure during an exposure process;

FIG.5 depicts an acid distribution control of a photoresist layer on a film structure with a desired profile during a post exposure baking process; and

FIG.6 is a flow diagram of one method of control acid distribution of a photoresist layer during an exposure process.

To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the Figures. Additionally, elements of one embodiment may be advantageously adapted for utilization in other embodiments described herein.

DETAILED DESCRIPTION

Methods for enhancing profile control of a photoresist layer formed by photolithography are provided. The diffusion of acid generated by a photoacid generator during a post-exposure bake procedure that contributes to line edge/width roughness may be mitigated by utilizing a film structure disposed under the photoresist layer as disclosed herein. The electric field application controls the diffusion and distribution of the acids generated by the photoacid generator in the photoresist layer as well as in an underlayer disposed in a film structure under the photoresist layer, thus preventing the line edge/width roughness that results from random diffusion. Methods for forming a film structure disposed under the photoresist layer utilized to control aforementioned acid distribution and diffusion are disclosed herein.

FIG.2 is a schematic cross-sectional view of an apparatus for processing a substrate, according to one embodiment. As shown in the embodiment ofFIG.2, the apparatus may be in the form of avacuum processing chamber200. In other embodiments, theprocessing chamber200 may not be coupled to a vacuum source.

Theprocessing chamber200 may be an independent stand alone processing chamber. Alternatively, theprocessing chamber200 may be part of a processing system, such as, for example, an in-line processing system, a cluster processing system, or the track processing system as needed. Theprocessing chamber200 is described in detail below and may be used for a pre-exposure bake, a post-exposure bake, and/or other processing steps.

Theprocessing chamber200 includeschamber walls202, anelectrode assembly216, and asubstrate support assembly238. Thechamber walls202 includesidewalls206, alid assembly210, and abottom208. Thechamber walls202 partially enclose aprocessing volume212. Theprocessing volume212 is accessed through a substrate transfer port (not shown) configured to facilitate movement of asubstrate240 into and out of theprocessing chamber200. In embodiments where theprocessing chamber200 is part of a processing system, the substrate transfer port may allow for thesubstrate240 to be transferred to and from an adjoining transfer chamber.

Apumping port214 may optionally be disposed through one of thelid assembly210,sidewalls206 orbottom208 of theprocessing chamber200 to couple theprocessing volume212 to an exhaust port. The exhaust port couples thepumping port214 to various vacuum pumping components, such as a vacuum pump. The pumping components may reduce the pressure of theprocessing volume212 and exhaust any gases and/or process by-products out of theprocessing chamber200. Theprocessing chamber200 may be coupled to one ormore supply sources204 for delivering one or more source compounds into theprocessing volume212.

Thesubstrate support assembly238 is centrally disposed within theprocessing chamber200. Thesubstrate support assembly238 supports thesubstrate240 during processing. Thesubstrate support assembly238 may comprise abody224 that encapsulates at least one embeddedheater232. In some embodiments, thesubstrate support assembly238 may be an electrostatic chuck. Theheater232, such as a resistive element, is disposed in thesubstrate support assembly238. Theheater232 controllably heats thesubstrate support assembly238 and thesubstrate240 positioned thereon to a predetermined temperature. Theheater232 is configured to quickly ramp the temperature of thesubstrate240 and to accurately control the temperature of thesubstrate240. In some embodiments, theheater232 is connected to and controlled by thepower source274. Thepower source274 may alternatively or additionally apply power to thesubstrate support assembly238. Thepower source274 may be configured similarly to thepower source270, discussed below. Furthermore, it is noted that theheater232 may be disposed from other locations of theprocessing chamber200, such as from chamber wall, chamber liner, edge ring that circumscribes the substrate, the chamber ceiling and the like, as needed to provide thermal energy to thesubstrate240 disposed on thesubstrate support assembly238

In some embodiments, thesubstrate support assembly238 may be configured to rotate. In some embodiments, thesubstrate support assembly238 is configured to rotate about the z-axis. Thesubstrate support assembly238 may be configured to continuously or constantly rotate, or thesubstrate support assembly238 may be configured to rotate in a step-wise or indexing manner. For example, thesubstrate support assembly238 may rotate a predetermined amount, such as 90°, 180°, or 270°, and then rotation may stop for a predetermined amount of time.

Generally, thesubstrate support assembly238 has afirst surface234 and asecond surface226. Thefirst surface234 is opposite thesecond surface226. Thefirst surface234 is configured to support thesubstrate240. Thesecond surface226 has astem242 coupled thereto. Thesubstrate240 may be any type of substrate, such as a dielectric substrate, a glass substrate, a semiconductor substrate, or a conductive substrate. Thesubstrate240 may have amaterial layer245 disposed thereon. Thematerial layer245 may be any desired layer. In other embodiments, thesubstrate240 may have more than onematerial layer245. Thesubstrate240 also has aphotoresist layer250 disposed over thematerial layer245. Thesubstrate240 has been previously exposed to electromagnetic radiation in an exposure stage of a photolithography process. Thephotoresist layer250 haslatent image lines255 formed therein from the exposure stage. Thelatent image lines255 may be substantially parallel. In other embodiments, thelatent image lines255 may not be substantially parallel. Also as shown, thefirst surface234 of thesubstrate support assembly238 is separated from theelectrode assembly216 by a distance d in the z-direction. Thestem242 is coupled to a lift system (not shown) for moving thesubstrate support assembly238 between an elevated processing position (as shown) and a lowered substrate transfer position. The lift system may accurately and precisely control the position of thesubstrate240 in the z-direction. In some embodiments, the lift system may also be configured to move thesubstrate240 in the x-direction, the y-direction, or the x-direction and the y-direction. Thestem242 additionally provides a conduit for electrical and thermocouple leads between thesubstrate support assembly238 and other components of theprocessing chamber200. A bellows246 is coupled to thesubstrate support assembly238 to provide a vacuum seal between theprocessing volume212 and the atmosphere outside theprocessing chamber200 and facilitate movement of thesubstrate support assembly238 in the z-direction.

Thelid assembly210 may optionally include aninlet280 through which gases provided by thesupply sources204 may enter theprocessing chamber200. Thesupply sources204 may optionally controllably pressurize theprocessing volume212 with a gas, such as nitrogen, argon, helium, other gases, or combinations thereof. The gases from thesupply sources204 may create a controlled environment within theprocessing chamber200. Anactuator290 may be optionally coupled between thelid assembly210 and theelectrode assembly216. Theactuator290 is configured to move theelectrode assembly216 in one or more of the x, y, and z directions. The x and y directions are referred to herein as the lateral directions or dimensions. Theactuator290 enables theelectrode assembly216 to scan the surface of thesubstrate240. Theactuator290 also enables the distance d to be adjusted. In some embodiments theelectrode assembly216 is coupled to thelid assembly210 by a fixed stem (not shown). In other embodiments, theelectrode assembly216 may be coupled to the inside of the bottom208 of theprocessing chamber200, to thesecond surface226 of thesubstrate support assembly238, or to thestem242. In still other embodiments, theelectrode assembly216 may be embedded between thefirst surface234 and thesecond surface226 of thesubstrate support assembly238.

Theelectrode assembly216 includes at least afirst electrode258 and asecond electrode260. As shown, thefirst electrode258 is coupled to apower source270, and thesecond electrode260 is coupled to anoptional power supply275. In other embodiments, one of thefirst electrode258 and thesecond electrode260 may be coupled to a power supply and the other electrode may be coupled to a ground. In some embodiments, thefirst electrode258 and thesecond electrode260 are coupled to a ground and thepower source274 that delivers power to the substrate support is a bipolar power supply that switches between a positive and negative bias. In some embodiments, thepower source270 or thepower supply275 may be coupled to both thefirst electrode258 and thesecond electrode260. In other embodiments, thepower source270 or thepower supply275 may be coupled to thefirst electrode258, thesecond electrode260, and thesubstrate support assembly238. In such embodiments, the pulse delay to each of thefirst electrode258, thesecond electrode260, and thesubstrate support assembly238 may be different. Theelectrode assembly216 may be configured to generate an electric field parallel to the x-y plane defined by the first surface of thesubstrate support assembly238. For example, theelectrode assembly216 may be configured to generate an electric field in one of the y direction, x direction or other direction in the x-y plane.

Thepower source270 and thepower supply275 are configured to supply, for example, between about 500 V and about 100 kV to theelectrode assembly216, to generate an electric field having a strength between about 0.1 MV/m and about 100 MV/m. In some embodiments, thepower source274 may also be configured to provide power to theelectrode assembly216. In some embodiments, any or all of thepower source270, thepower source274, or thepower supply275 are a pulsed direct current (DC) power supply. The pulsed DC wave may be from a half-wave rectifier or a full-wave rectifier. The DC power may have a frequency of between about 10 Hz and 1 MHz. The duty cycle of the pulsed DC power may be from between about 5% and about 95%, such as between about 20% and about 60%. In some embodiments, the duty cycle of the pulsed DC power may be between about 20% and about 40%. In other embodiments, the duty cycle of the pulsed DC power may be about 60%. The rise and fall time of the pulsed DC power may be between about 1 ns and about 1000 ns, such as between about 10 ns and about 500 ns. In other embodiments, the rise and fall time of the pulsed DC power may be between about 10 ns and about 100 ns. In some embodiments, the rise and fall time of the pulsed DC power may be about 500 ns. In some embodiments, any or all of thepower source270, thepower source274, and thepower supply275 are an alternating current power supply. In other embodiments, any or all of thepower source270, thepower source274, and thepower supply275 are a direct current power supply.

In some embodiments, any or all of thepower source270, thepower source274, and thepower supply275 may use a DC offset. The DC offset may be, for example, between about 0% and about 75% of the applied voltage, such as between about 5% and about 60% of the applied voltage. In some embodiments, thefirst electrode258 and thesecond electrode260 are pulsed negatively while thesubstrate support assembly238 is also pulsed negatively. In these embodiments, thefirst electrode258 and thesecond electrode260 and thesubstrate support assembly238 are synchronized but offset in time. For example, thefirst electrode258 may be at the “one” state while the substrate support assembly is at the “zero” state,” then thesubstrate support assembly238 in the one state while thefirst electrode258 is at the zero state.

Theelectrode assembly216 spans approximately the width of thesubstrate support assembly238. In other embodiments, the width of theelectrode assembly216 may be less than that of thesubstrate support assembly238. For example, theelectrode assembly216 may span between about 10% to about 80%, such as about 20% and about 40%, the width of thesubstrate support assembly238. In embodiments where theelectrode assembly216 is less wide than thesubstrate support assembly238, theactuator290 may scan theelectrode assembly216 across the surface of thesubstrate240 positioned on thefirst surface234 of thesubstrate support assembly238. For example, theactuator290 may scan such that theelectrode assembly216 scans the entire surface of thesubstrate240. In other embodiments, theactuator290 may scan only certain portions of thesubstrate240. Alternatively, thesubstrate support assembly238 may scan underneath theelectrode assembly216.

In some embodiments, one ormore magnets296 may be positioned in theprocessing chamber200. In the embodiment shown inFIG.1, themagnets296 are coupled to the inside surface of thesidewalls206. In other embodiments, themagnets296 may be positioned in other locations within theprocessing chamber200 or outside theprocessing chamber200. Themagnets296 may be, for example, permanent magnets or electromagnets. Representative permanent magnets include ceramic magnets and rare earth magnets. In embodiments where themagnets296 include electromagnets, themagnets296 may be coupled to a power source (not shown). Themagnets296 are configured to generate a magnetic field in a direction perpendicular or parallel to the direction of the electric field lines generated by theelectrode assembly216 at thefirst surface234 of thesubstrate support assembly238. For example, themagnets296 may be configured to generate a magnetic field in the x-direction when the electric field generated by theelectrode assembly216 is in the y-direction. The magnetic field drives the charged species355 (shown inFIG.3) and polarized species (not shown) generated by the photoacid generators in thephotoresist layer250 in a direction perpendicular to the magnetic field, such as the direction parallel with the latent image lines255. By driving the chargedspecies355 and polarized species in a direction parallel with thelatent image lines255, line roughness may be reduced. The uniform directional movement of the chargedspecies355 and polarized species is shown by the double headedarrow370 inFIG.3. In contrast, when a magnetic field is not applied, the chargedspecies355 and polarized species may move randomly, as shown by thearrows370′.

Continuing to refer toFIG.3, theelectrode assembly216 includes at least thefirst electrode258 and thesecond electrode260. Thefirst electrode258 includes afirst terminal310, afirst support structure330, and one ormore antennas320. Thesecond electrode260 includes asecond terminal311, asecond support structure331, and one ormore antennas321. Thefirst terminal310, thefirst support structure330, and the one ormore antennas320 of thefirst electrode258 may form a unitary body. Alternatively, thefirst electrode258 may include separate portions that may be coupled together. For example, the one ormore antennas320 may be detachable from thefirst support structure330. Thesecond electrode260 may similarly be a unitary body or be comprised of separate detachable components. Thefirst electrode258 and thesecond electrode260 may be fabricated by any suitable technique. For example, thefirst electrode258 and thesecond electrode260 may be fabricated by machining, casting, or additive manufacturing.

Thefirst support structure330 may be made from a conductive material, such as metal. For example, thefirst support structure330 may be made of silicon, polysilicon, silicon carbide, molybdenum, aluminum, copper, graphite, silver, platinum, gold, palladium, zinc, other materials, or mixtures thereof. Thefirst support structure330 may have any desired dimensions. For example, the length L of thefirst support structure330 may be between about 25 mm and about 450 mm, for example, between about 100 mm and about 300 mm. In some embodiments, thefirst support structure330 has a length L approximately equal to a diameter of a standard semiconductor substrate. In other embodiments, thefirst support structure330 has a length L that is larger or smaller than the diameter of a standard semiconductor substrate. For example, in different representative embodiments, the length L of thefirst support structure330 may be about 25 mm, about 51 mm, about 76 mm, about 100 mm, about 150 mm, about 200 mm, about 300 mm, or about 450 mm. The width W of thefirst support structure330 may be between about 2 mm and about 25 mm. In other embodiments, the width W of thefirst support structure330 is less than about 2 mm. In other embodiments, the width W of thefirst support structure330 is greater than about 25 mm. The thickness of thefirst support structure330 may be between about 1 mm and about 10 mm, such as between about 2 mm and about 8 mm, such as about 5 mm. In some embodiments, thefirst support structure330 may be square, cylindrical, rectangular, oval, rods, or other shapes. Embodiments having curved exterior surfaces may avoid arcing.

Thesupport structure330 may be made of the same materials as thesecond support structure331. The range of dimensions suitable for thefirst support structure330 is also suitable for thesecond support structure331. In some embodiments, thefirst support structure330 and thesecond support structure331 are made of the same material. In other embodiments, thefirst support structure330 and thesecond support structure331 are made of different materials. The lengths L, widths W, and thicknesses of thefirst support structure330 and thesecond support structure331 may be the same or different.

The one ormore antennas320 of thefirst electrode258 may also be made from a conductive material. The one ormore antennas320 may be made from the same materials as thefirst support structure330. The one ormore antennas320 of thefirst electrode258 may have any desired dimensions. For example, a length L1 of the one ormore antennas320 may be between about 25 mm and about 450 mm, for example, between about 100 mm and about 300 mm. In some embodiments, the one ormore antennas320 have a length L1 approximately equal to the diameter of a standard substrate. In other embodiments, the length L1 of the one ormore antennas320 may be between about 75% and 90% of the diameter of a standard substrate. A width W1 of the one ormore antennas320 may be between about 2 mm and about 25 mm. In other embodiments, the width W1 of the one ormore antennas320 is less than about 2 mm. In other embodiments, the width W1 of the one ormore antennas320 is greater than about 25 mm. The thickness of the one ormore antennas320 may be between about 1 mm and about 10 mm, such as between about 2 mm and about 8 mm. The one ormore antennas320 may have a cross-section that is square, rectangular, oval, circular, cylindrical, or another shape. Embodiments having round exterior surfaces may avoid arcing.

Each of theantennas320 may have the same dimensions. Alternatively, some of the one ormore antennas320 may have different dimensions than one or more of theother antennas320. For example, some of the one ormore antennas320 may have different lengths L1 than one or more of theother antennas320. Each of the one ormore antennas320 may be made of the same material. In other embodiments, some of theantennas320 may be made of a different material thanother antennas320.

Theantennas321 may be made of the same range of materials as theantennas320. The range of dimensions suitable for theantennas320 is also suitable for theantennas321. In some embodiments, theantennas320 and theantennas321 are made of the same material. In other embodiments, theantennas320 and theantennas321 are made of different materials. The lengths L1, widths W1, and thicknesses of theantennas320 and theantennas321 may be the same or different.

Theantennas320 may include between 1 and about 40antennas320. For example, theantennas320 may include between about 4 and about 40antennas320, such as between about 10 and about 20antennas320. In other embodiments, theantennas320 may include more than 40antennas320. In some embodiments, each of theantennas320 may be substantially perpendicular to thefirst support structure330. For example, in embodiments where thefirst support structure330 is straight, eachantenna320 may be substantially parallel to thefirst support structure330. Each of theantennas320 may be substantially parallel to each of theother antennas320. Each of theantennas321 may be similarly positioned with respect to thesupport structure331 and eachother antenna321.

Each of theantennas320 has aterminal end323. Each of theantennas321 has aterminal end325. A distance C is defined between thefirst support structure330 and theterminal end325. A distance C′ is defined between thesecond support structure331 and theterminal end323. Each of the distances C and C′ may be between about 1 mm and about 10 mm. In other embodiments, the distances C and C′ may be less than about 1 mm or greater than about 10 mm. In some embodiments, the distance C and the distance C′ are equal. In other embodiments, the distance C and the distance C′ are different.

A distance A is defined between facing surfaces of one of theantennas321 and an adjacent one of theantennas321. The distance A′ is defined between facing surfaces of oneantenna320 and an adjacent one theantennas320. The distances A and A′ may be greater than about 6 mm. For example, the distances A and A′ may be between about 6 mm and about 20 mm, such as between about 10 mm and about 15 mm. The distances A and A′ between eachadjacent antennas321,320 may be the same or different. For example, the distances A′ between the first and second, second and third, and third and fourth antennas of the one ormore antennas320 may be different. In other embodiments, the distances A′ may be the same.

A distance B is defined between facing surfaces of one of theantennas320 and an adjacent one of theantennas321. The distance B may be, for example, greater than about 1 mm. For example, the distance B may be between about 2 mm and about 10 mm, such as between about 4 mm and about 6 mm. Each distance B may be the same, each distance B may be different, or some distances B may be the same and some distances B may be different. Adjusting the distance B allows for easy control of the electric field strength.

Theantennas320,321 may be oriented in an alternating arrangement above thephotoresist layer250. For example, theantennas320 of thefirst electrode258 and theantennas321 of thesecond electrode260 may be positioned such that at least one of theantennas320 is positioned between two of theantennas321. Additionally, at least oneantenna321 may be positioned between two of theantennas320. In some embodiments, all but one of theantennas320 is positioned between two of theantennas321. In those embodiments, all but one of theantennas321 may be positioned between two of theantennas320. In some embodiments, theantennas320 and theantennas321 may each have only one antenna.

In some embodiments, thefirst electrode258 has afirst terminal310, and thesecond electrode260 has asecond terminal311. Thefirst terminal310 may be a contact between thefirst electrode258 and thepower source270, thepower supply275, or a ground. Thesecond terminal311 may be a contact between thesecond electrode260 and thepower source270, thepower supply275, or a ground. Thefirst terminal310 and thesecond terminal311 are shown as being at one end of thefirst electrode258 and thesecond electrode260, respectively. In other embodiments, thefirst terminal310 and thesecond terminal311 may be positioned at other locations on thefirst electrode258 and the second electrode, respectively. Thefirst terminal310 and thesecond terminal311 have different shapes and sizes than thefirst support structure330 and thesupport structure331, respectively. In other embodiments, thefirst terminal310 and thesecond terminal311 may have generally the same shapes and sizes as thefirst support structure330 and thesupport structure331, respectively.

In operation, a voltage may be supplied from a power supply, such as thepower source270, thepower source274, or thepower supply275, to thefirst terminal310, thesecond terminal311, and/or thesubstrate support assembly238. The supplied voltage creates an electric field between each antenna of the one ormore antennas320 and each antenna of the one ormore antennas321. The electric field will be strongest between an antenna of the one ormore antennas320 and an adjacent antenna of the one ormore antennas321. The interleaved and aligned spatial relationship of theantennas320,321 produces an electric field in a direction parallel to the plane defined by thefirst surface234 of thesubstrate support assembly238. Thesubstrate240 is positioned on thefirst surface234 such that thelatent image lines255 are parallel to the electric field lines generated by theelectrode assembly216. Since the chargedspecies355 are charged, the chargedspecies355 are affected by the electric field. The electric field drives the chargedspecies355 generated by the photoacid generators in thephotoresist layer250 in the direction of the electric field. By driving the chargedspecies355 in a direction parallel with thelatent image lines255, line edge roughness may be reduced. The uniform directional movement is shown by the double headedarrow370. In contrast, when a voltage is not applied to thefirst terminal310 or thesecond terminal311, an electric field is not created to drive the chargedspecies355 in any particular direction. As a result, the chargedspecies355 may move randomly, as shown by thearrows370′, which may result in wariness or line roughness.

FIG.4 depicts afilm structure404 disposed on asubstrate400 during a lithography exposure process. Aphotoresist layer407 is disposed on thefilm structure404. Thefilm structure404 includes anunderlayer405 disposed on ahardmask layer403 and further on atarget layer402. Thetarget layer402 is later patterned for forming the desired device features in thetarget layer402. In one example, theunderlayer405 may be an organic material, an inorganic material, or a mixture of organic or inorganic materials. In the embodiment wherein theunderlayer405 is an organic material, the organic material may be a cross-linkable polymeric material that may be coated onto thesubstrate400 through a spin-on process, and then thermally cured so that thephotoresist layer407 may be later applied thereon. In the embodiment wherein theunderlayer405 is an inorganic material, the inorganic material may be a dielectric material formed by any suitable deposition techniques, such as CVD, ALD, PVD, spin-on-coating, spray coating or the like.

Theunderlayer405 functions as a planarizing layer, an antireflective coat and/or photoacid direction controller, which may provide etch resistance and line edge roughness control when transferring the pattern into theunderlying hardmask layer403 and thetarget layer402. The patterning resistant functionality from theunderlayer405 may work with theunderlying hardmask layer403 during the transfer of the resist process. In one example, theunderlayer405 does not interact with thephotoresist layer407 and does not have interfacial mixing and/or diffusion or cross contamination with thephotoresist layer407.

Theunderlayer405 includes one or more additives, such as acid agents, (e.g., photoacid generators (PAGs) or acid catalyst), base agents, adhesion promoters or photo-sensitive components. The one or more additives may be disposed in organic solvent or resin and/or an inorganic matrix material. Suitable examples of the acid agents including photoacid generators (PAGs) and/or acid catalyst selected from a group consisting of sulfonic acids (e.g., p-toluenesulfonic acid, styrene sulfonic acid), sulfonates (e.g., pyridinium p-toluenesulfonate, pyridinium trilluoromethanesulfonate, pyridinium 3-nitrobenzensulfonate), and mixtures thereof. Suitable organic solvent may include homo-polymers or higher polymers containing two or more repeating units and polymeric backbone. Suitable examples of the organic solvent include, but are not limited to, propylene glycol methyl ether acetate (PGMEA), ethyl lactate (EL), propylene glycol methyl ether (PGME), propylene glycol n-propyl ether (PnP), cyclohexanone, acetone, gamma butyrolactone (GBL), and mixtures thereof.

In one example, theunderlayer405 provides active acid agents, base agents or ironoic/non-ironic species during the lithographic exposure process, pre- or post-exposure baking process, to assist control the photoacid flowing direction from theupper photoresist layer407.

Thehardmask layer403 may be an ARC layer fabricated from a group consisting of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, amorphous carbon, doped amorphous carbon, TEOS oxide, USG, SOG, organic silicon, oxide containing material titanium nitride, titanium oxynitride, combinations thereof and the like.

Thephotoresist layer407 may be a positive-tone photoresist and/or a negative-tone photoresist that are capable of undergoing a chemically amplified reaction. Thephotoresist layer407 is a polymer organic material.

As discussed above, an electric field from the electrode116, as well as a magnetic field from themagnets296, may be applied during a lithography exposure process, pre- or post-exposure baking process, particularly, a post exposure baking process. In the example depicted inFIG.4, the electric field and/or and magnetic field is applied during a lithography exposure process. During the lithographic exposure process, alight radiation412 is directed to afirst region408 of thephotoresist layer407 while with asecond region406 of thephotoresist layer407 protected by aphotomask410. Photoacid, shown as e⁻ inFIG.4, is generated in the exposedfirst region408 in thephotoresist layer407 when photoacid generator (PAG) is exposed to thelight radiation412, such as a UV light radiation. However, oftentimes, movement of photoacid are generally random and photoacid distribution may not be evenly distributed in thefirst region408 or may not have a clear boundary set at theinterface430 formed in a plane (interfaced with the second region406) defining between thefirst region408 and thesecond region406, resulting in portion of photoacid drifting and diffusing into thesecond region406, as shown in thearrow422, unintended to have photoacid generation. As such, lateral photoacid movement (e.g., a direction parallel to a planar surface of the substrate400) drifted into thesecond region406, as shown in thearrow422, may result in line edge roughness, resolution loss, photoresist footing, profile deformation, thus causing inaccurate feature transfer to theunderlying target layer402 and/or eventually leading to device failure.

Although the example discussed here is shown as the movement of electrons from the photoacid, it is noted that any suitable species, including charges, charged particles, photons, ions, electrons, or reactive species in any forms, may also have similar effects when the electric field is applied to thephotoresist layer407.

By applying an electric field and/or magnetic field to thephotoresist layer407, distribution of photoacid in the exposedfirst region408 may be efficiently controlled and confined. The electric field as applied to thephotoresist layer407 may move photoacid in a vertical direction (e.g., y direction shown byarrows416 and420 substantially perpendicular to the planar surface of the substrate400) with minimal lateral motion (e.g., x direction shown by the arrow422) without diffusing into the adjacentsecond region406. Generally, photoacid may have certain polarity that may be effected by the electric field or magnetic field applied thereto, thus orienting photoacid in certain directions, thus creating a desired directional movement of the photoacid in the exposedfirst region408 without crossing into the adjacent protectedsecond region406. In one example, the photoacid may further be controlled to move directionally at a longitudinal direction (e.g., z direction shown byarrow428, defined in a plane interfaced with thesecond region406 of thephotoresist layer407 protected by the photomask410) along a lateral plane, as shown byarrow414, so as to control the longitudinal distribution of photoacid confined in the exposedfirst region408 without crossing at a x direction, as shown byarrow422, into thesecond region406 of thephotoresist layer407. The magnetic field generated to thephotoresist layer407 may cause the electrons to orbit along a certain magnetic line, such as the longitudinal direction (e.g., z direction shown by arrow428) so as to further control the photoacid in a desired three-dimensional distribution. The interaction between the magnetic field and the electric field may optimize trajectory of photoacid at a certain path as desired and confined in the exposedfirst region408. Furthermore, vertical photoacid movement is desired to smooth out standing waves that are naturally produced by the light exposure tool, thus enhancing exposure resolution. In one embodiment, an electric field having a strength between about 0.1 MV/m and about 100 MV/m may be applied to thephotoresist layer407, during a lithographic exposure process, pre- or post baking process, to confine photoacid generated in thephotoresist layer407 in a vertical direction, e.g., at a y direction. In one embodiment, a magnetic field of between 0.1 Tesla (T) and 10 Tesla (T), along with the electric field, may be applied to thephotoresist layer407, during a lithographic exposure process, pre- or post baking process, to confine photoacid generated in thephotoresist layer407 in both longitudinal direction and vertical direction, e.g., at y and z directions, with minimum lateral direction, e.g., at x direction. While in combination of the magnetic field along with the electric field, the photoacid as generated may be further confined to be distributed in the longitudinal direction, e.g., in the direction shown by thearrow428, remaining in thefirst region408 of thephotoresist layer407, parallel along theinterface430 within the exposedfirst region408.

FIG.5 depicts another profile of photoacid distribution that may be controlled by utilizing an electric field, magnetic field, or combinations thereof to specifically control the photoacid located at certain zones during a post exposure baking process. The exposedregion502 of thephotoresist layer407 has chemically altered from thefirst region408 as shown inFIG.4, after the lithographic exposure process. After thephotoresist layer407 is lithographically exposed, a post exposure baking process is then performed to cure thephotoresist layer407, including the exposedregion502 and the remaining regions (e.g., shielded by the photomask during the lithographic exposure process) in thephotoresist layer407. During the post exposure baking process, the acid agent (e.g., such as photoacid), base agent, or other suitable additive from theunderlayer405 may be controlled in a manner that can assist distribution/movement of the photoacid within thephotoresist layer407 in a desired direction, as shown by thearrow506 inFIG.5. The additive in theunderlayer405 is diffused to theupper photoresist layer504 during the post exposure baking process (or even during the lithographic exposure process), which helps to improve the sensitivity of thephotoresist layer407 so as to maintain a vertical profile of thephotoresist layer407. As a result, after development and rinse, a substantially vertical profile may be obtained in thephotoresist layer407.

In one embodiment, the additives, such as acid agents or photoacid as one example, from theunderlayer405 may be thermally driven upwards, as shown by thearrow506, during the post exposure baking process so that the profile of thephotoresist layer407 may be efficiently controlled. Furthermore, as the additives from theunderlayer405 may be driven at a particular direction upward by the electric field, magnetic field, or combinations thereof during the post exposure baking process, the electrons provided from the additives may be controlled at certain moving path, such as predominantly in a vertical direction toward thephotoresist layer407. By doing so, the desired vertical structure may be defined and confined in thephotoresist layer407 as needed. It is noted that the examples of thephotoresist layer407 depicted inFIGS.4-5 are formed with a straight edge profile (e.g., a vertical sidewall). However, the profile of thephotoresist layer407 may be formed in any desired shapes, such as a tapered or flare-out opening as needed.

After the post exposure baking process, an anisotropic etching process, or other suitable patterning/etching processes, may be performed to transfer features into theunderlayer405, thehardmask layer403 and thetarget layer402 as needed.

FIG.6 depicts a flow diagram of amethod600 for utilizing an underlayer disposed under a photoresist layer to assist controlling photoacid distribution/diffusion in a photoresist layer during a lithographic exposure process or during a pre- or a post-exposure baking process. Themethod600 beings atoperation602 by positioning a substrate, such as thesubstrate400 described above, into a processing chamber, such as theprocessing chamber200 depicted inFIGS.2-3, with an electrode assembly and a magnetic assembly disposed therein.

Atoperation604, after thesubstrate400 is positioned, an electric field and/or a magnetic field may be individually or collectively applied to the processing chamber (during a lithographic exposure process and/or post exposure baking process) to control photoacid movement within in a photoresist layer having an underlayer disposed thereunder. After the electric field and/or a magnetic field is individually or collectively applied to the photoresist layer and the underlayer disposed on the substrate, photoacid as generated may move primarily in a vertical direction, a longitudinal direction, a circular direction, rather than a lateral direction. As a result of the assistance provided by the underlayer disposed under the photoresist layer, the photoacid movement in the photoresist layer may be efficiently controlled.

Atoperation606, after the exposure process, a post exposure baking process is performed to cure the photoresist layer and the underlayer. During the baking process, an energy (e.g., an electric energy, thermal energy or other suitable energy) may also be provided to the underlayer. In one example depicted here, the energy is a thermal energy provided to the substrate during the post exposure baking process. The additives from the underlayer may also assist controlling the flow direction of the photoacid within the photoresist layer. By utilizing directional control of photoacid distribution in a predetermined path having a patterned photoresist layer, a desired edge profile with high resolution, does sensitivity, resistance to line collapse, and stochastics failure, and minimum line edge roughness may be obtained. In one example, by utilizing the underlayer structure, the critical dimension uniformity (CDU) (e.g., critical dimension variation) may be reduced from generally from 3 nm to 6 nm down to 1 nm to 2 nm or less, which is about 50% to 600% uniformity improvement. The line width roughness (LWR) may be reduced from generally from 3 nm to 5 nm down to 1 nm to 2 nm or less, which is about 50% to 600% roughness improvement. Furthermore, a distance between a first tip end of a first trench to a second tip end of a second trench may be reduced from generally from 30 nm to 50 nm down to 10 nm to 20 nm. Furthermore, some types of defects, such as corner rounding, footing, deformed profile, slanted sidewall profile, may also be efficiently eliminated and reduced.

The previously described embodiments have many advantages, including the following. For example, the embodiments disclosed herein may reduce or eliminate line edge/width roughness with high resolution and sharp edge profile. The aforementioned advantages are illustrative and not limiting. It is not necessary for all embodiments to have all the advantages.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims (15)

What is claimed is:

1. A method of processing a substrate, the method comprising:

applying a photoresist layer comprising a photoacid generator to on a multi-layer film structure disposed on a substrate, wherein the multi-layer film structure comprises an underlayer, the underlayer comprising an organic solvent and an acid agent selected from the group consisting of a sulfonic acid, a sulfonate, and a mixture thereof;

exposing a first portion of the photoresist layer unprotected by a photomask to a radiation light in a lithographic exposure process; and

applying an electric field or a magnetic field to alter movement of photoacid generated from the photoacid generator substantially in a vertical direction.

2. The method ofclaim 1, further comprising:

baking the photoresist layer and the underlayer; and

applying an electric field or a magnetic field while baking the photoresist layer and the underlayer.

3. The method ofclaim 1, wherein the electric field or the magnetic field is applied to the photoresist layer during the lithographic exposure process.

4. The method ofclaim 2, wherein applying the electric field further comprises:

performing a pre-exposure baking process to the photoresist layer and the underlayer disposed on the substrate, wherein the electric field or the magnetic field is applied to the photoresist layer during the pre-exposure baking process.

5. The method ofclaim 1, wherein the underlayer comprises one or more additives in an organic polymer solvent.

6. The method ofclaim 5, wherein the underlayer further comprises an additive comprising a base agent, adhesion promotor and photo-sensitive component, or any combination thereof.

7. The method ofclaim 5, wherein the organic polymer solvent is selected from the group consisting of propylene glycol methyl ether acetate (PGMEA), ethyl lactate (EL), propylene glycol methyl ether (PGME), propylene glycol n-propyl ether (PnP), cyclohexanone, acetone, gamma butyrolactone (GBL), and mixtures thereof.

8. The method ofclaim 1, wherein the multi-layer film structure further comprises a hardmask layer disposed under the underlayer and above the substrate.

9. The method ofclaim 8, wherein the hardmask layer is selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, amorphous carbon, doped amorphous carbon, TEOS oxide, USG, SOG, organic silicon, oxide containing material titanium nitride, titanium oxynitride, and combinations thereof.

10. A method of processing a substrate, the method comprising:

applying a photoresist layer on an underlayer disposed on a substrate, the underlayer comprises an organic solvent and an acid agent selected from the group consisting of a sulfonic acid, a sulfonate, and a mixture thereof;

exposing a first portion of the photoresist layer unprotected by a photomask to a radiation light in a lithographic exposure process;

performing a baking process on the photoresist layer and the underlayer; and

applying an electric field or a magnetic field while performing the baking process.

11. The method ofclaim 10, wherein exposing the first portion of the photoresist layer further comprises:

applying an electric field or a magnetic field while performing the lithographic exposure process.

12. The method ofclaim 10, wherein the underlayer is an organic material.

13. The method ofclaim 10, wherein the underlayer further comprises an additive comprising a base agent, an adhesion promotor a photo-sensitive component, or any combination thereof.

14. The method ofclaim 10, wherein applying the electric field or the magnetic field while performing the baking process further comprises:

altering movement of photoacid generated in the photoresist layer substantially in a vertical direction.

15. The method ofclaim 10, wherein applying the electric field or the magnetic field while performing the baking process further comprises:

orienting photoacid in the photoresist layer while performing the baking process.

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